The mast is deck stepped.
On the traverse back to the cockpit, the lines have to travel uphill over about a 10 inch rise in the cabin roof. So my idea for the collar is that the spring blocks, when standing will be at the perfect height for the lines to travel right at the cabin roof level.
I may have a set screw or two to stop upward travel.
My main concern here is the top and bottom collar edge forces trying to crimp the mast as the blocks are loaded with the lines.
I have seen pictures of metal mast collars. These are usually thin (height wise) affairs, but are anchored with multiple screws. The loading is on the screws.
Here the loading will be of the teak against the mast surface.
I think if I make it thick enough (height wise) the creasing forces on the top and bottom teak edges deminish?
Would 3 inches be too thin?